1. Field of the Invention
This invention relates to lubricating grease compositions and more particularly to improved lubricating grease compositions containing additives such as the rare earth halides.
2. Description of the Prior Art
Over the years, the development of a satisfactory lubricating grease composition for use under extreme pressure, high temperature and high speed conditions has received widespread attention. Consequently, numerous additives have been proposed to enhance the physical and chemical properties of grease compositions. Additives which have been proposed for producing such grease compositions include lead-sulfur additives, heavy metal sulfide additives, particularly molybdenum disulfide additives, soluble phosphorus-sulfur additives, and, more recently, oil insoluble phosphorus-oil soluble sulfur additives. These additives, although providing some effectiveness under extreme pressure conditions, have certain disadvantages, both functional and economical. For example, molybdenum disulfide, which is generally accepted as an additive for producing extreme pressure lubricants and greases, is relatively expensive and increases the cost of manufacturing said lubricants and greases. Also, with additives such as those mentioned above which contain sulfur, there is the possibility of additive breakdown and degradation under severe and/or extreme conditions, resulting in the release of sulfur. Metal parts in contact with grease compositions containing sulfur in a free or combined state can, in time, cause serious corrosion to metal parts.
U.S. Pat. No. 3,453,209 discloses solid lubricating compositions for use with metal-forming dyes, for example, presses, forges, drop hammers and the like. Suitable lubricants disclosed by the reference are the zinc, molybdenum and cadmium sulfides, tungsten disulfide, graphite and inorganic fluorides, such as calcium fluoride.
U.S. Pat. No. 3,492,229 relates to jet engine lubricants, heat transfer fluids and hydraulic fluids having oxidation resistance properties. These lubricants contain an alkali metal compound or an antimony, bismuth or lanthanum compound, such as lanthanum oxide.
U.S. Pat. No. 3,525,690 discloses grease compositions which comprise a base fluid of hexafluoropropylene epoxide and a thickener selected from ammeline, boron nitride particles and a fluorocarbon resin or particle.
U.S. Pat. No. 3,684,711 relates to hydraulic fluids, heat transfer fluids and lubricants which contain a complex alkali metal organophosphorus compound or a complex rare earth metal organophosphorus compound as an oxidation inhibitor.
U.S. Pat. No. 4,034,133 discloses a magnetic recording element which includes a base and a coating upon the surface of the base, which comprises magnetic particles dispersed in a polymeric binder and a lubricant. The lubricant is described as a trifluoride of cerium, lanthanum, praseodymium, neodymium and samarium.
As can readily be determined from the above, there is an ongoing effort to develop new lubricant compositions.
Accordingly, it is an object of the present invention an improved grease composition.
Another object of the present invention is to provide a grease composition having an improved load carrying ability.
Yet another object of the present invention is to provide a lubricating composition having improved extreme pressure properties.
These and other objects are accomplished according to the present invention by adding a rare earth metal halide to a lubricating composition.